svn commit: r318995 - head/sys/vm

[Alan Cox]

Author: alc
Date: Sat May 27 16:40:00 2017
New Revision: 318995
URL: https://svnweb.freebsd.org/changeset/base/318995

Log:
  In r118390, the swap pager's approach to striping swap allocation over
  multiple devices was changed.  However, swapoff_one() was not fully and
  correctly converted.  In particular, with r118390's introduction of a per-
  device blist, the maximum swap block size, "dmmax", became irrelevant to
  swapoff_one()'s operation.  Moreover, swapoff_one() was performing out-of-
  range operations on the per-device blist that were silently ignored by
  blist_fill().
  
  This change corrects both of these problems with swapoff_one(), which will
  allow us to potentially increase MAX_PAGEOUT_CLUSTER.  Previously,
  swapoff_one() would panic inside of blist_fill() if you increased
  MAX_PAGEOUT_CLUSTER.
  
  Reviewed by:	kib, markj
  MFC after:	3 days

Modified:
  head/sys/vm/swap_pager.c

Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c	Sat May 27 14:07:46 2017	(r318994)
+++ head/sys/vm/swap_pager.c	Sat May 27 16:40:00 2017	(r318995)
@@ -2310,9 +2310,13 @@ swapoff_one(struct swdevt *sp, struct uc
 	 */
 	mtx_lock(&sw_dev_mtx);
 	sp->sw_flags |= SW_CLOSING;
-	for (dvbase = 0; dvbase < sp->sw_end; dvbase += dmmax) {
+	for (dvbase = 0; dvbase < nblks; dvbase += BLIST_BMAP_RADIX) {
+		/*
+		 * blist_fill() cannot allocate more than BLIST_BMAP_RADIX
+		 * blocks per call.
+		 */
 		swap_pager_avail -= blist_fill(sp->sw_blist,
-		     dvbase, dmmax);
+		    dvbase, ulmin(nblks - dvbase, BLIST_BMAP_RADIX));
 	}
 	swap_total -= (vm_ooffset_t)nblks * PAGE_SIZE;
 	mtx_unlock(&sw_dev_mtx);